The aim of the proposed research is to understand how elements of the cytoskeleton interact with the cell membrane in carrying out various cellular activities. To obtain the structural information required for this understanding, the uniquely well ordered arrangement of a membrane-microtubule complex from the algae Euglenophyceae will be taken advantage of. The three-dimensional structure of this complex will be determined from electron micrographs of the isolated membrane by Fourier methods of analysis. The protein components responsible for binding the microlubule to the membrane will be identified, and their functional equivalents in cells of higher animals located. The pathway by which cells assemble and take apart these complexes will be analyzed. Results from this work are expected to significantly enhance our understanding of how the cell's membrane and its cytoskeleton work together in such important cellular processes as division, movement, phagocytosis, and positioning of surface receptors.